1. Field of the Invention
The invention relates to a liquid crystal on silicon display (LCOS display), and more particularly, to an LCOS display having color filters positioned on the top surface of the cover substrate.
2. Description of the Prior Art
LCOS display technology is the key of reflective LCOS projectors and rear-projection televisions. The advantages of LCOS micro-displays are a tiny size, high resolution, low power, low cost, etc. The difference between an LCOS display and a conventional thin film transistor-liquid crystal display (TFT-LCD) is materials used for forming substrates. Both a cover substrate and a backplane are made of glass in a TFT-LCD. Nevertheless, the cover substrate in an LCOS display is made of glass, but the backplane in an LCOS display is a semiconductor silicon substrate. Therefore, an LCOS process combines LCD techniques and complementary metal-oxide semiconductor (CMOS) processes.
The main structure of an LCOS display includes a light source module, an LCOS panel, and a color separation and combination optical system. Generally speaking, the LCOS display can be divided into three-panel LCOS displays and single-panel LCOS displays according to the type of optical engine. The three-panel type optical engine separates lights generated from light source into red, blue, and green lights through a plurality of prisms, projects those lights into three separated LCOS panels respectively, and combines those three lights from LCOS panels to form colored images. The single-panel type optical engine utilizes a color wheel to form red, blue, and green lights sequentially from white lights, and synchronizes the three kinds of lights with single-colored images, the red, blue, and green images, formed by driving programs so as to produce color-separated images sequentially. Since human eyes have the persistence of vision, people can see colored images from the projected images.
Please refer to FIG. 1, which is a schematic diagram of a portion of an LCOS panel 10 according to the prior art. The LCOS panel 10 comprises a semiconductor substrate 12 with pluralities of MOS transistors and pixel electrodes (not shown) thereon, a glass substrate 14 positioned in parallel with and opposite to the semiconductor substrate 12, a liquid crystal layer 16 positioned between the semiconductor substrate 12 and the glass substrate 14, and a transparent conductive layer 18 positioned on the liquid crystal layer 16. Generally, a conventional LCOS panel 10 comprises an anti-reflective (AR) coating 22 positioned on the upper surface of the glass substrate 14, which is a light exit surface or a display surface of the LCOS panel 10, and two alignment layers (not shown) positioned on the top and bottom sides of the liquid crystal layer 16. The conventional LCOS panel 10 may further comprise a color filter 20 positioned between the transparent conductive layer 18 and the glass substrate 14 or between the alignment layer above the liquid crystal layer 16 and the transparent conductive layer 18.
However, no matter if the color filter 20 is positioned between the glass substrate 14 and the transparent conductive layer 18, or between the transparent conductive layer 18 and the alignment in the prior art, it causes a disadvantage of heat generated by the color filter 20 when the LCOS panel 10 is operating accumulating in the inner portion of the LCOS panel 10 because the heat cannot be removed by an outer cooling system easily. Consequently, the longevity of the elements of the LCOS panel 10 decreases. Therefore, how to design a structure of the LCOS panel for improving the performance of heat radiation so as to extend the longevity of the elements of the LCOS panel is still an important issue for manufacturers.